1. Field of the Invention
The present invention relates to a method and a terminal for selecting an access point (AP).
2. Discussion of the Related Art
A 3GPP that establishes a technology standard of a 3rd generation mobile communication system has started a research into long term evolution/system architecture evolution (LTE/SAE) technology as part of an effort to optimize and improve performance of 3 GPP technologies from the end of 2004 in order to cope with various forums and new technologies associated with 4th generation mobile communication.
SAE that is progressed around 3GPP SA WG2 is a research into network technology to determine a structure of a network with an LTE work of a 3GPP TSG RAN and support mobility between model networks and one of key standardization issues of the 3GPP. This is a work for developing a 3GPP system to a system that supports various wireless access technologies based on an IP and the work has been progressed for the purpose of an optimized packet based system that minimizes a transmission delay with a further improved data transmission capability.
An SAE higher-level reference model defined in the 3GPP SA WG2 includes a non-roaming case and a roaming case of various scenarios, and a detailed content may be referred in TS 23.401 and TS 23.402 which are 3GPP standard documents. A network structure diagram of FIG. 1 shows schematic reconfiguration of the SAE higher-level reference model.
FIG. 1 is a Structural Diagram of an Evolved Mobile Communication Network.
One of largest features of the network structure of FIG. 1 is based on a 2 tier model of eNodeB of an evolved UTRAN and a gateway of a core network and although accurately matches each other, the eNodeB 20 has functions of NodeB and RNC of an existing UMTS system and the gateway has an SGSN/GGSN function of the existing system.
Another key feature is that a control plane and a user plane between an access network and the core network are exchanged to different interfaces. In the existing UMTS system, one lu interface exists between an RNC and an SGSN, while a mobility management entity (MME) 51 that undertakes processing of a control signal has a structure separated from a gateway (GW), and as a result, two interfaces of S1-MME and S1-U are respectively used. The GW includes a serving-gateway (hereinafter, referred to as ‘S-GW’) 52 and a packet data network gateway (hereinafter, referred to as ‘PDN-GW’ or ‘P-GW’) 53.
Meanwhile, in recent years, congestion of a core network of a mobile communication provider has been aggravated with an explosive increase of data. As a scheme for relieving the aggravated congestion, there is a discussion intended to offload data of a user terminal to a wired network without passing through a core network of a provider. As a result of such a discussion, technologies such as IP flow mobility and seamless offload (IFOM), multi access PDN connectivity (MAPCON), etc. for supporting multiple radio access have been proposed. The MAPCON technology establishes PDN connections through their preferred radio access such as 3GPP access or Wi-Fi access and transmits data through the PDN connections. The IFOM technology allows a PDN connection to use 3GPP access and Wi-Fi access simultaneously and transmits data through their preferred access.
FIG. 2A is an Exemplary Diagram Illustrating an Example of IFOM Technology.
Referring to FIG. 2A, the IFOM provides the same PDN connection through various different accesses simultaneously. The IFOM provides offloading to a seamless WLAN.
Further, the IFOM transfers an IP flow of one same PDN connection from one access to another access.
FIG. 2B is an Exemplary Diagram Illustrating an Example of MAPCON Technology.
As known with reference to FIG. 2B, the MAPCON technology easily connects IP flows of various PDN connections to other APNs through different access systems.
According to the MAPCON technology, a UE 10 may create a new PDN connection on an access which is not previously used. Alternatively, the UE 10 may create a new PDN connection to one selected from various accesses which are previously used. Alternatively, the UE 10 may transfer all or some of all PDN connections which are already connected to another access.
Technology associated with Wi-Fi interworking includes traffic offloading technology and technology associated with WLAN selection. That is, technology in which a terminal can automatically select a WLAN is standardized (3GPP TS 24.234) and an associated operation is described below. First, the terminal searches neighboring Wi-Fi to create a list of available WLANs. This is a list of SSIDs expressing the WLANs. The created list and a preferred WLAN list are compared with each other to select the most preferred WLAN in the created list. An ANQP query is transmitted to the selected WLAN to acquire PLMN information which is providable by the WLAN. The most preferred PLMN (for example, Home PLMN) is selected by comparing the acquired PLMN information to preferred PLMN information which is stored in advance and is used to access to the corresponding PLMN through an authentication process.
FIG. 3 Illustrates an Environment in which a General AP and a Recently Discussed Hotspot 2.0 AP are Present.
An traditional HotSpot meant that a Wi-Fi service is provided to an unspecific majority in a public place where a floating population is large. However, with a recent explosive increase in a bandwidth usage, it is difficult to sufficiently provide a bandwidth required as 3rd generation or 4th generation mobile communication technology now. In particular, in a commercial area in which a population is dense during the daytime, bandwidth management is actually impossible and a HotSpot 2.0 that makes a mobile communication network in a population dense area interwork with a Wi-Fi network to provide a Vertical Handoff service is researched in order to solve such a problem.
The HotSpot 2.0 as a standard developed in Wi-Fi Alliance (WFA) aims at simplifying and automating access to a public Wi-Fi network. A mobile terminal aims at recognizing which AP among various neighboring access points is suitable for a usage purpose thereof and authenticating the corresponding AP from a remote service provider by using appropriate credentials. To this end, the respective APs is allowed to provide new various information, and information indicating whether a specific service provider is connectable, a HotSpot provider, a roaming consortium, Venue information (Venue Group, Venue Type), configuration information can be provided.
Herein, the roaming consortium is a group of service providers that make a roaming agreement. Numerous service set identifiers (SSIDs) that are managed for each roaming consortium may be present according to the roaming consortium and a 3GPP provider who cooperates with the roaming consortium may not know all of numerous SSIDs. Accordingly, a HotSpot 2.0 AP 40c provides roaming consortium information to increase efficiency of management instead of the numerous SSIDs.
The roaming consortium information is constituted by a list of a service provider or a company or an agency that made a roaming agreement with the service provider. Herein, information of each company or agency is expressed as an organizational unique identifier (OUI). That is, the roaming consortium information is configured in a list form of OUI1, OUI2, . . . , OUI_n. Herein, the OUI can be used by being registered in IEEE, and is information which is unique for each agency. Further, the HotSpot 2.0 AP 40c may provide BSS load information or bandwidth information (for example, WAN Metrics).
Meanwhile, as illustrated, under a situation in which the hotspot 2.0 AP 40c and general APs 40a and 40b coexist, the UE 10 receives SSID information from the general APs 40a and 40b and the roaming consortium information from the hotspot 2.0 AP 40c. 
However, since a 3GPP release 11 based UE 10 which has been developed up to now may select only the general APs 40a and 40b based on only the SSID and may not read the roaming consortium information, the UE 10 may not select the hotspot 2.0 AP 40c. 
In detail, the UE 10 provides only SSID information in order to select the AP in a 3GPP network in prior art. According to 3GPP release 11, AP selection, that is, WLAN selection has been developed aiming at selecting a public land mobile network (PLMN). As a result, the UE 10 receives SSIDs broadcasted from the APs 40a and 40b to create an available list and thereafter, accesses respective APs in order of the SSIDs selected by comparing a preference list stored in advance and information on the created list and reads PLMN list information supported by the APs. The PLMN information is also compared with a preference PLMN list to select a PLMN having the highest preference. When the PLMN selection is completed, the AP is accessed by using the corresponding SSID to access the corresponding PLMN.
As described above, since the 3GPP release 11 based UE 10 which has been developed up to now may select only the general APs 40a and 40b based on only the SSID and may not select the hotspot 2.0 AP 40c. 